1. Field of the Invention
This invention relates generally to methods for forming thin films comprising tellurium (Te) on a substrate surface. Such films may be, for example, antimony-telluride (Sb—Te), germanium-telluride (Ge—Te), or germanium-antimony-telluride (Ge—Sb—Te) thin films.
2. Description of the Related Art
Te thin films such as Sb—Te, Ge—Te, and Ge—Sb—Te thin films are used in many different applications, including phase-change non-volatile electronic memories and optical storage materials. While many different phase change memory (PCM) cells are known, the operation of PCM cells comprising Te alloys is based on the resistivity difference between amorphous and crystalline states of the material. A resistivity difference of more than three orders of magnitude can be obtained by many different phase change alloys. The switching in a PCM cell is generally accomplished by heating the material locally with suitable current pulses, which, depending on the intensity of the pulse, leave the material in a crystalline or amorphous state. A wide variety of different PCM cell structures exist, many of which use trench or pore-like structures formed by sputtering.
Finding suitable Te precursors compatible with ALD processes has been challenging as many precursors do not result in film growth and/or are extremely toxic. Te hydride reactants, such as H2Te, are typically highly toxic gases, which can be difficult to use. Te alkyl derivatives, such as R2Te, are less toxic and less volatile; however, they are typically not as reactive as the Te hydrides.
A need exists for methods for controllably and reliably forming thin films comprising Te, particularly antimony-telluride, germanium-telluride, and germanium-antimony-telluride thin films.